The OLED (Organic Light Emitting Diode) as a current type light emitting device is more and more applied to high performance display areas due to its characteristics such as self light emitting, fast response, wide angle of view and ability of being fabricated on a flexible substrate.
Different from liquid crystal displays which use stable voltage to control brightness, OLED is current-driven, and needs a stable current to control light emitting. For OLED display, how to address the impact of the threshold voltage shift is one of the concerns that need to be focus on when designing pixel circuits.
Meanwhile, in recent years, the touch control function is more and more widely applied in various display panels, especially in mobile display, and has almost become the standard configuration for smart phones. Accordingly, OLED display panels with touch control functions have been more and more popular in people of all ages. But now, in the known art, the display panel and TSP (touch screen panel) are often fabricated separately, and then jointed together. Such a procedure causes the process of the display panel with touch screen to be complex and of high cost, and is not advantageous for the lightness and thinness of display. TSP in cell (TSP built-in) technology integrates the display function and the touch control function, which uses one process, instead of two divided processes, to complete. Therefore, it not only has the advantage of low cost, but also makes the process simple and the display touch panel more light and thin. But as to how to perfectly integrate the touch control circuit with the pixel circuit, there is still no good solution.